This disclosure generally relates to turbine systems, and in particular to methods used in manufacturing components for turbine systems.
Turbines are devices that generate rotary mechanical power from the energy in a stream of moving fluid. Turbines may be used in aircraft, watercraft (both marine and fresh water), various types of land-based turbines, and the like. Turbine components are generally fabricated from superalloys, for example alloys of nickel (Ni), iron (Fe), or cobalt (Co). Temperature constraints of such superalloys, particularly single-crystal nickel-based superalloys, however, limit their use in turbine engines in which extreme temperature conditions may be experienced.
In order to overcome the temperature limitations of these superalloys, newer materials based on niobium (Nb) have been developed. The niobium based materials are termed niobium based refractory metallic-intermetallic composites (hereinafter Nb based RMICs). The Nb based RMICs have melting temperatures greater than 1700° C., which exceeds the current temperature service limits of Ni-based superalloys.
The high melting temperatures of the Nb based RMICs however presents some problems during the manufacturing of components having intricate geometries, especially components for turbine systems. For example, when intricate components are sought to be manufactured through processes such as casting, preferred micro-structures within the component are often not achieved because of a lack of control over the solidification conditions. Another drawback of components manufactured from Nb based RMICs is the additional internal machining required after molding to create hollow structures or other complex geometries. The additional post-molding machining increases the time of production as well as the expenditure incurred in the manufacture of such components because of the complex nature of the production equipment. It is therefore generally desirable to be able to manufacture turbine components that have long lifetimes at service temperatures of about 700° C. to about 1370° C., and that can have complex geometries without substantial additional post-molding machining. It is also desirable to have a turbine system having components constructed from Nb based RMIC composites wherein intricate features may be achieved in a simple manufacturing process and wherein suitable control of the microstructure is achieved during processing.